System and portable device for transmitting identification signals

ABSTRACT

The invention relates to a system with a portable device for the transmission of a signal to a second device, wherein the portable device is wearable on the body of a user. The portable device includes at least two electrodes and transmitter electronics for the generation of an electrical signal between the electrodes, such that the signal is able to be coupled by the electrodes into the body of the user and detected by at least one electrode of the second device. A portable device or also a second device (receiver) is distinguished in that at least one of the electrodes is at least partially transparent.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the communication between a sender(transmitter) and a receiver over a capacitive coupling (sometimes alsoreferred to as capacitive resistive coupling, “intrabody” coupling,RCID-coupling or PAN-coupling) in which small electrical currents whichare used for the transmission of information between the transmitter andthe receiver are generated in the human body, and/or in which thetransmitter and the receiver interact with one another over very shortdistances via electric fields.

2. Description of Related Art

This method of coupling is disclosed in the U.S. Pat. Nos. 4,591,854,5,914,701 and 5,796,827. Implementations thereof are described in theinternational patent application PCT/CH 2006/000518 as well as infurther published specifications of various authors.

A particular advantage of the capacitive coupling through the human bodyor, as the case may be, over short distances is the selectivity of thedata transmission. Depending on the configuration, one can determinewith a high degree of certainty that the signal received by the receivercan only have been transmitted by the person who is situated in directproximity to or in physical contact with a receiver electrode that isdesignated for it.

A disadvantage is, among other things, that as a result of the poorsignal to noise ratio (literally: signal-to-interference ratio), only asmall amount of data can be transmitted. A good signal to noise ratio isonly possible with a large amplitude of the transmission signal.However, a large amplitude (i.e. high voltage) would rather not betolerated by the user. In the international patent publication WO2007/112609, approaches are described, with which these problems can beaddressed. Despite these, the bandwidth of the signal transmissionremains limited.

The layout of the electrodes in the transmitter is important for aseffective a signal transmission as possible. According to the state ofthe art, these are designed as electrode pairs, wherein the twoelectrodes lie parallel and opposite one another in the manner of aplate capacitor. The electrodes should be as large as possible so as tomaximize the coupling into the body and also to optimize the signal tonoise ratio, in the situation in which no electrically conductivecontact exists between the one electrode and the human body. However,these large electrodes have a problematic effect on the design and thedimensions of the transmitter. Furthermore, they cause the powerconsumption of the transmitter to be quite high, so that more frequentbattery changing is necessary.

With this background in mind, it is an object of the present inventionto provide solutions for the layout of transmitter electrodes whichameliorate the above-mentioned disadvantages at least partly and whichmean a further step toward the commercial application of the technologyand its acceptance by consumers. The solutions mentioned should inparticular be usable for access control.

These objects will be achieved by the invention, as it is described inthe claims.

BRIEF SUMMARY OF THE INVENTION

According to the invention, a portable device or also a receiver ischaracterized in that at least one of the electrodes is at leastpartially transparent.

A portable device according to the approach according to the inventionis, for example, wearable on the body of a user; it can, for example, bedesigned as a card-like identification medium, as a “smart card cover”,mobile telephone, watch, portable computer (for example of the “handheldcomputer” type). It includes at least two electrodes and means for thecreation of an electrical signal between the electrodes, such that thesignal is able to be coupled through the electrodes into the body of theuser and is detectable from the body by at least one electrode of asecond device. Such a device also makes possible a direct, short-rangecommunication (not through the body), for example through holding of theportable device in direct proximity of a receiver electrode, i.e.applications of the invention are not limited to coupling through thehuman body but rather also extend to cases in which the user carries theportable device on his or her person, holds it in the vicinity of areceiver electrode or otherwise makes it possible that the communicationbetween transmitter and receiver takes place directly and notexclusively over the body.

Transparent electrical conductors, for example of very thin layers ofmetal that are vacuum-metalized or applied via a sputter depositiontechnique on a transparent substrate, or certain doped semiconductors onan oxide base (TCOs as for example ITO-layers), are currently available.For a considerable time already, these have been well-known for certainapplications, for example as components for flat-screen displays orthin-film solar cells. They have not yet been considered for informationtransmission, as they are known to have poor electrical conductivity andwould result in unacceptably large losses when used with the highfrequencies usually employed in information transmission.

However, it has now been recognized that the capacitive resistiveinformation transmission is configurable such that the conductivecapacity of transparent electrodes is adequate. In particular, thecombination of comparatively low voltages (for example less than 5V oreven less than 3V) and currents and low frequencies (for example lessthan a 2 MHz center frequency) allows the use of the electrodes withlimited conductive capacity. Moreover, it has somewhat surprisingly beenrecognized that these conductive layers can be used as electrodes,without significantly impairing the read and write capabilities of aRFID transponder used in combination with the capacitive resistiveinformation transmission, even if the respective RFID antenna issituated between the electrodes and, for example, is substantiallysurrounded by the electrodes.

Through the amazingly simple technique according to the invention, manynew degrees of freedom arise with respect to the design of a receiver ora transmitter, for example of fully transparent buttons, or buttons withan underlying display mechanism.

Preferably—in particular for applications in which it is used for accesscontrol (for example the operation of door locks and/or the release ofobjects as for example instruments, possibly including data logging)—thetransmitter (and/or possibly a receiver) is situated in a portabledevice. Until now, for portable devices, the design seemed to be lessimportant, since a portable device of the type according to theinvention is generally carried in a bag or otherwise covered while worn.A further realization of the invention is that with the introduction oftransparent electrodes, the design possibilities of portable devicesmultiply considerably:

-   -   Arrangement of the electrodes as layers on a card, comprising a        label or labels—in the manner of an identification card or a        “badge”, possibly with a photo—as well as possibly comprising        further functionalities. The electrodes can form the outermost        layers—with the exception of, if necessary, thin protective        layers—of the card.    -   Arrangement of the electrodes in a holder (“shell”, “cover”) for        a smart card. Smart cards are often used as so-called “badges”        for the control of access. In the process, they are introduced        into transparent holders, which for example are attachable to a        piece of clothing by means of a clip and are visible from the        outside. According to the first aspect of the invention, it is        now possible to form this holder out of rigid or flexible        material as part of the transmitter. This arrangement has the        additional advantage that the capacitance of the capacitor        arrangement formed by the two electrodes is reduced, as will be        described in greater detail below.    -   Combination with a different electronic device, for example a        mobile telephone. Modern electronic devices often have large        displays. According to the invention a first of the two sender        (and/or receiver) electrodes can be arranged in or over the        display. This also has the advantage of a reduced capacitance,        if the second—transparent or not transparent—electrode is for        example arranged in the area of a back side of the device.        Furthermore, this results in multifaceted possible combinations        of the functionality, as will be described below in more detail.

In all of these cases, elements of the transmitter electronics and/orelements of other applications can be arranged between the transparentelectrodes. A special application envisions the arrangement of a RFIDtag (RFID transponder with antenna) between the transparent electrodes.As already mentioned, the electrodes can even substantially cover theRFID antenna without substantially influencing the functionality of theRFID application.

Furthermore, the allowance for transparent electrodes has theparticularly attractive advantage for the “access control” applicationthat one does not notice the electrode, or even that it is an electrodeand therefore a part of an electronic device. Rather, depending on thedesign, it seems to be simply a shell, a design element or anotherfunctional element.

According to a preferred form of the invention, the two electrodes of aportable device (transmitter) are arranged such that between theelectrodes there are arranged either component parts of the transmitterelectronics and/or of another application distinct from the transmitterelectronics—therein can also be designated a battery—or an air gap ispresent, in which such a component part—for example with a “smart card”as carrier of the component part—can be inserted.

Component parts here are meant to be active or passive preferablyelectronic component parts, which are more than a mere separating layerbetween the electrodes, for example in particular active electroniccomponent parts such as ASICs, processors, integrated circuits, memorymodules, sender and/or receiver for contact-free informationtransmission, including active or passive RFID transponders, passivecomponent parts such as antennas, resistors, capacitors, coils, etc. oralso batteries, optical elements etc.

Of course the transmitter electronics and electronic component parts forthe application which is distinct from the transmitter electronics maybe integrated together with one another in at least one unifiedcomponent—for example in an integrated circuit. The feature of the“component part of an application which is distinct from the transmitterelectronics” is simply that between the electrodes are arrangedelectronic elements which can administrate functions that are entirelyseparate from the capacitive resistive information transmission andpreferably from other contact-free information transmission methods, forexample as they control or constitute the display of a mobile telephoneor as they store information and/or have stored information which is notcommunicated with the intrabody information transmission, etc.

This approach makes use of the recent finding that for the transmissionof data, the area of the electrodes is important, however not thecapacitive coupling there-between. On the contrary, it has been foundthat for a given electrode size a large capacitance is unfavorable,because a large capacitance creates a negative effect on the life of abattery of the portable device, since larger currents flow in thegeneration of signals. Furthermore, as a result of the larger flowingcurrent of larger capacitance, the requirements on the electrodeconductivity are higher. It has further been found that a parallelarrangement of the electrodes is indeed a possibility, but is notnecessary.

In the case of a plate capacitor, the capacitance is proportional to thearea of the electrodes and to the dielectric constant of the materialbetween the electrodes, but inversely proportional to the distancebetween the electrodes. As a result of the approach according thepreferred embodiment, the two electrodes are in general farther apartfrom one another than according to the state of the art, without thisprecluding a compact design of the portable device. Through the largerelectrode separation, the capacitance is limited. In combination withthe transparent electrodes with their comparatively limited electricconductivity this results in a synergy effect, because such transparentelectrodes are particularly good to use as a result of their smallerflowing current.

In embodiments in which between the electrodes there is an air gap inwhich the components of a distinct application—for example an identitycard and/or smart card—are able to be inserted, the compatibility withexisting systems as well as backwards compatibility are also a given.

According to a special embodiment of the invention, the portable devicewith the air gap can comprise a communications interface, over whichdata can be exchanged with the application that is inserted into the airgap. Such an interface can, for example, be formed like a conventionalsmart card reader.

According to a further special embodiment, a communication link canexist between the transmitter electronics and an input unit, wherein thesignals transmitted by the transmitter electronics can be dependent ondata that are input. For example, the transmitted signal can include aPIN, which the user previously has input in the input unit. In thisembodiment, the portable device can, for example, be designed as amobile telephone, wherein the input unit can correspond to the inputunit of the mobile telephone (keypad, touch screen, voice recognitiondevice etc.).

Particularly preferably, in this embodiment the display of the mobiletelephone is furnished or covered with a transparent electrode.

If the portable device is a mobile telephone, the electrical supply forthe transmitter electronics can be obtained by simple means: namely asthe transmitter electronics are energized by the very powerful batteryof the mobile telephone, for example over a 3V DC supply. Thecommunication between the transmitter electronics and the remainingelectronic component parts of the mobile telephone can beaccomplished—in case these are not integrated with one another—over anyknown or yet to be developed interface, for example over a I²C data bus.

The receiver includes at least one receiver electrode and evaluationelectronics, through which a signal that is generated by the capacitiveresistive signal transmission is detectable between the receiverelectrode and a further electrode or between the receiver electrode anda ground closure, and can be evaluated.

Particularly preferable is the use of an information transmissionmethod, which relies on the spread spectrum method, wherein the signalis transmitted as an ultra-broadband signal, preferably according to theteaching of WO 2007/112609. Ultra-broadband is defined as the use of afrequency range of a bandwidth of at least 20% of the center frequencyor, as the case may be, carrier frequency. According to the teaching ofthis document, in particular a direct sequence spread spectrum is used.The data are preferably first modulated with a method of digital datamodulation and subsequently spectrum-spread. In WO 2007/112609, methodsare also described for the analysis of a capacitive resistive signal.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, embodiments of the invention are illustrated by meansof schematic figures. Shown are:

FIG. 1 a depiction of a transmitter according to the invention;

FIG. 2 a depiction of a transmitter according to the invention with asmart card of a further application inserted;

FIG. 3 a sectional view of a transmitter with smart card;

FIG. 4 a depiction of an automobile interior with transparent receiverelectrodes;

FIG. 5 a mobile telephone in a form according to the invention; and

FIG. 6 a schematic of the mobile telephone from FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

The portable device 1 according to FIG. 1 is in the depicted exampledesigned to be substantially card-shaped and comprises a first electrode3 and a second electrode 4. Between the first and the second electrodeare arranged further elements, for example a plastic carrier 5 withintegrated and/or applied electronic component parts and a batterycompartment (not depicted in the figure). The integrated and/or appliedelectronic component parts can, for example, include an ASIC for thecontrol of the electrodes, EEPROM or EPROM memory, conductive pathwaysand/or further elements. Rather than plastic, the carrier can be ofceramic, of fabric or of a different material, the important factor issimply that the two electrodes are electrically isolated from oneanother.

According to the first aspect of the invention, now at least one of theelectrodes is at least partly transparent, in the depicted example, thefirst electrode 3. On an upper side of the plastic carrier 5, letters,pictures, etc. can be applied by known means such that they are visiblethrough the transparent electrode.

FIG. 2 depicts an illustrative example that according to a preferredembodiment comprises, between the electrodes, an air gap in which hereare inserted elements of a further application. The transmitter 1 isdesigned as a so-called “smart card cover”. Smart card covers are assuch known to those skilled in the art. They are designed as, forexample, rigid, transparent shells, which for example can be attached toa piece of clothing and in which a smart card (i.e. a card-shaped mediumwith memory and communication functionalities) is able to be inserted.

The transmitter comprises a compartment for a battery 6 as well ascontrol electronics, here represented schematically by a chip 7, for theat least partly transparent electrodes 3, 4. The smart card 11 is ableto be inserted into an air gap. A possible inscription area 12 of thesmart card remains visible behind the transparent first electrode 3.

FIG. 3 depicts a variant of the embodiment from FIG. 2, in which thesmart card (or as the case may be other component part of thetransmitter electronics of a distinct application) simultaneously servesas RFID identification medium. In addition to the elements alreadydescribed, one sees schematically the RFID antenna 15, which here is notcompletely covered by one of the electrodes—in the depicted example bythe transparent electrode 3. The RFID communication also functions,however, if otherwise than as depicted in the figure, both transparentelectrodes completely cover the RFID antenna 15, i.e. if the transparentelectrode 3 covers the entire upper surface shown in the figure.

In FIG. 4 the dashboard of an automobile is depicted very schematically,in which and/or on which a plurality of receiver electrodes arearranged. The automobile is driven by a user, into whom a transmitter isable to couple a capacitive resistive data signal. The transmitter can,for example, be worn by the user and individually customized for him, orit can also be situated at a site necessarily contacted by the user—forexample in the seat. The personalized variant is particularlypreferable.

The dashboard comprises, in a known manner, display panels 21 andcontrols 22. In addition, it features a plurality of receiver electrodes23, 24 which function as input surfaces. A contact upon a receiverelectrode by the user—in which as mentioned a data signal is continuallycoupled—is registered by a controller of the receiver electrode. Thiscontroller has a communication link with the automobile electronics,through which a corresponding event can be triggered, for example theturning-on of a turn signal or a low-beam headlight etc. This event canbe dependent on the user—for example a control surface can have adifferent function for a first user than for a second user, or it can bethat other parameters, for example seat adjustments etc. are selected.The user selectivity results from the fact that the first and the seconduser can be assigned different transmitters and thus differentcapacitive resistive data signals. Obviously, it can also be imaginedthat a particular user is altogether not authorized to operate thevehicle functions or only authorized for specific times/for a particularnumber of inputs.

A transference from automobiles to other objects—for example buildingsetc.—is of course also possible.

According to the invention, now at least one of the receiver electrodes23, 24 are transparent, for example at least those receiver electrodes24 that cover a display field. Through these surprisingly simpleapproaches, new possibilities for interaction arise, for example in thata set speed for a cruise control can be set directly on the speedometer.Transparent receiver electrodes—for example all receiver electrodes aretransparent—can be rear-projected upon and/or labeled by a correspondingdisplay field depending on the situation.

FIGS. 5 and 6 relate to a portable device according to the inventionthat is designed as a mobile telephone 31. The first electrode 3 isintegrated into the display and is at least in the area of the displaytransparent, while the second electrode 4, as in the previous examplesof transmitter electrodes, is not necessarily transparent. The secondelectrode is situated on a reverse side of the mobile telephone (orrather as in the depicted example on the clamshell lid or on a differentpart of the mobile telephone) and can as the case may be, also be formedby a conductive section of the housing. It is arranged at as large afixed distance away from the first electrode as possible. In FIG. 6 itis very schematically depicted how the transmitter electronics 7 canhave a connection to the remaining mobile telephone electronics: themobile telephone supplies the transmitter electronics (3V), and acommunication link exists over a I²C interface.

The integration of the transmitter electronics 7 in a mobile telephonemakes possible the integration of several functionalities with oneanother in one portable device. The following are for example possible:

-   -   Dynamic alteration of the capacitive resistive transmitted data        signals. The active data signal can for example be used as a PIN        code, which can be altered arbitrarily often.    -   Increased security can be made possible, for example through        so-called “rolling codes” or other known means of secure data        transmission.    -   An even further increased security can be achieved as the UHF        transmission means of mobile telephones (Bluetooth, 3G et.) is        included in the information transmission procedure, for example        as a downlink. This makes possible for example the use of known        “challenge-response” systems. A central unit can also be        included into communication and, for example, issue certificates        (Cerberus etc.).    -   The mobile telephone with the transmitter electronics can be        used as a programming device. A continuous data stream can be        sent to the receiver with the help of the transmitter        electronics.    -   Future mobile telephones will perhaps be furnished with NFC,        RFID or low-power-wireless (for example as distributed under the        brand name Wibree™ (www.wibree.com)) or Ultra Low Power        Bluetooth or other standards of identification. Through the use        of the capacitive resistive information transmission such an        identification technology can be integrated into a single        device, and the user must not necessarily know which technology        is in actuality used. Particularly interesting is the        combination of the approach according to the invention with        other things, because for example, the selective capacitive        resistive information transmission follows a short-range (<10 m)        contactless nonselective information transmission, and can work        together with this.    -   Transmitter electronics for a mobile telephone can be designed        according to standard dimensions and may be integrated in        existing mobile telephone architecture without further ado.

1.-16. (canceled)
 17. A system for the transmission of signals, thesystem comprising: a first, portable device, which is wearable by auser, and a second device, wherein the first and the second devicecomprise means for the transmission of information signals at least fromthe first to the second device, the means for the transmission ofinformation comprising electrodes of the first device and at least oneelectrode of the second device and being equipped to couple informationinto the body of the user by the electrodes of the first device, and todetect the information signals by the electrode(s) of the second device,wherein at least one of an electrode of the first device and of anelectrode of the second device is at least partially transparent.
 18. Aportable device for the transmission of signals to a second device,wherein the portable device is wearable by a user, the portable devicecomprising: at least two electrodes and a signal generator for thegeneration of an electrical signal between the electrodes, such that thesignal is by means of the electrodes able to be coupled into the body ofthe user and able to be detected from the body by at least one electrodeof the second device, wherein at least one of the electrodes of theportable device is at least partly transparent.
 19. The portable deviceaccording to claim 18, wherein the portable device is designedsubstantially in a card shape and wherein the electrodes form layers ofthe substantially card-shaped device.
 20. The portable device accordingto claim 19, further comprising labeling.
 21. The portable deviceaccording to claim 20, wherein at least one of the electrodes istransparent and covers the labeling.
 22. The portable device accordingto claim 18, further comprising an antenna for communication by means ofinduction or over electromagnetic waves.
 23. The portable deviceaccording to claim 18, further comprising at least one of the groupcomprising: component parts of the transmitter electronics arrangedbetween the electrodes, components of another application distinct fromthe transmitter electronics arranged between the electrodes, and and anair gap between the electrodes.
 24. The portable device according toclaim 23, further comprising an air gap between the electrodes, whereinthe air gap has dimensions that are matched to those of an elementdistinct from the portable device, such distinct element being able tobe inserted into the air gap with an accurate fit.
 25. The portabledevice according to claim 23, wherein the distance between theelectrodes amounts to at least 1 mm.
 26. The portable device accordingto claim 25, wherein the distance between the electrodes amounts to atleast 1.5 mm.
 27. The portable device according to claim 26, wherein thedistance between the electrodes amounts to at least 2 mm.
 28. Theportable device according to claim 23, comprising an air gap between theelectrodes, the portable device further comprising, in the air gap, acommunications interface for the exchange of data between the portabledevice and a device that is distinct from the portable device, whichdistinct device and can be inserted into the air gap.
 29. The portabledevice according to claim 23, wherein a communications link exists orcan be formed between the transmitter electronics and an input unit, andthe transmitter electronics are designed and/or programmed such that theelectric signal is a function dependent upon the data that is input intothe input unit.
 30. The portable device according to claim 29, whereincomponent parts of an application distinct from the transmitterelectronics are arranged between the electrodes, and wherein theportable device is designed as a mobile telephone and the input unit isthe input unit of the mobile telephone.
 31. The portable deviceaccording to claim 30, wherein a display field of the mobile telephoneis furnished with or at least partly covered by the transparentelectrode or one of the transparent electrodes, respectively.
 32. Theportable device according to claim 18, wherein the signal generator isdesigned such that a maximal voltage between the electrodes does notexceed 5 V and/or wherein a center frequency of the generated signaldoes not exceed 2 MHz.
 33. A device for the reception of signals whichare coupled into the body of a user by electrodes of a first, portabledevice, comprising at least one electrode, wherein at least one of theelectrode(s) is/are at least partially transparent.
 34. The deviceaccording to claim 33, comprising a plurality of electrodes, wherein thedevice for the receiving of signals triggers different actions dependingupon which of the electrodes receives a signal.
 35. A method ofcontrolling access to an object, the method comprising the steps of:providing a system for the transmission of signals, the systemcomprising: a first, portable device, which is wearable by a user, and asecond device, wherein the first and the second device comprise meansfor the transmission of information signals at least from the first tothe second device, the means for the transmission of informationcomprising electrodes of the first device and at least one electrode ofthe second device and being equipped to couple information into the bodyof the user by the electrodes of the first device, and to detect theinformation signals by the electrode(s) of the second device, wherein atleast one of an electrode of the first device and of an electrode of thesecond device is at least partially transparent, the method furthercomprising the step of using the system for transmitting authenticationinformation between the first and the second device, and the step ofusing the authentication information to control the access.